Question

I’m having an issue where I call the result_array() function on n query object from in codeigniter:

   $this->db->select(array('a','b','c'));

   $query = $this->db->get('basic');
   print_r($query->list_fields());
   $test = $query->result_array();
   print_r($query->list_fields());

When I run this code, or:

   $query = $this->db->get('basic');
   print_r($query->list_fields());
   print_r($query->list_fields());

or:

   $query = $this->db->get('basic');
   $test = $query->result_array();
   print_r($query->list_fields());

The second list_fields() function always returns an array size 0, the first returns the correct list of field names.

In the last example where there is only one list_fields() function, the array is again size zero.

Any guidance in this matter will be greatly appreciated. I need the list_fields() function to be accessible after I read the result_array().

Here is the result of the first block of code:

    Array
    (
        [0] => site_id
        [1] => institution
        [2] => caller
        [3] => call_complete
        [4] => call_details
        [5] => id
        [6] => timestamp
    )
    Array
    (
    )

Thank you, for your help

Answer 1

That looks to be a bug in the database driver. For example, in CI_DB_mysqli_result:

public function list_fields()
{
    $field_names = array();
    while ($field = $this->result_id->fetch_field())
    {
        $field_names[] = $field->name;
    }

    return $field_names;
}

A subsequent call will return array() because the while loop seeks over all the fields and leaves the pointer at the end of the list.

However, in the result class, result_id is public, so you can use mysqli_result::field_seek:

$query = $this->db->get('basic');
var_dump($query->list_fields());

// this should be called before any call to list_fields()
$query->result_id->field_seek(0);
var_dump($query->list_fields());

However, this is bad practise, as this only works for mysqli; for mysql, you’ll need this:

mysql_field_seek($query->result_id, 0);

and for mssql:

mssql_field_seek($query->result_id, 0);

The correct way to do this is really to fix it in the database drivers. See this pull request 🙂